In underground high-voltage power distribution systems it will be appreciated that safety is always a primary concern. Whenever possible, line crews servicing components of the underground power distribution system must see a visible break between the high voltage cables and the electrical equipment prior to working on components of the system. To ensure their safety, line crews use insulated "hot sticks" to maintain a safe distance from the equipment as connections and disconnections are made between the high voltage cables and the equipment. If a visible break is not made between the cable and the equipment while working on the system, the line crew undertakes a very serious risk that the cable can be accidently re-energized and cause injury. As will be understood by the skilled artisan, the term "equipment" as used herein may be a transformer, switch, or junction product installed in a padmount enclosure or other high voltage environment.
An example of a known operating system used to connect and disconnect high voltage cables to and from equipment is schematically shown in FIGS. 1A-D and described below. As seen in FIG. 1A, a known operating system is generally designated by the numeral 10, and includes an equipment cabinet panel 12 upon which is mounted an appropriately rated equipment bushing 14. A 600 amp elbow connector, which is generally indicated by the numeral 16, is connected to the bushing 14 and includes a terminated high voltage cable 18. An appropriately rated load reducing tap plug 20 is installed in the other side of the elbow 16 while an insulating cap 24 is provided over the opposite end of the plug 20. FIG. 1A shows the operating system 10 in a normal energized condition.
Whenever work is required to be performed on the electrical equipment or any circuit or component connected downstream of the equipment, the operator(s) open a switch (not shown) that de-energizes the cable 18. Next, as seen in FIG. 1B, the operator removes the insulating cap 24 and inserts a test rod 26 into the load reducing tap plug 20 to confirm that the cable 18 is no longer energized. As seen in FIG. 1C, the operator next installs a grounding elbow or similar device 28 on to the load reducing tap plug 20. Should the cable 18 accidently become re-energized, the grounding elbow 28 shunts the current to ground and prevents excessive voltage from appearing on the cable 18 and possibly injuring the operator.
As stated previously, most operators are required to directly see that the portion of the underground power system that they are working on is clearly disconnected from the equipment. This also permits testing of the portion of the circuit being worked upon prior to re-energizing the circuit. In order to accomplish the physically visible break in the connection, reference is made to FIG. 1D. In particular, the grounding elbow 28 is removed from the plug 20 and one operator inserts a tool 30 held by a "hot stick" or insulated operating implement 32 into the plug 20. Simultaneously, a second operator uses another implement 32 to hold the elbow connector 16. The first operator rotates the tool 30 to disconnect an internally threaded connection in the elbow connector 16 from the equipment bushing 14. It will be appreciated that the second operator is required to hold the base of the elbow connector 16 to provide additional support as the first operator rotates the tool 30. Once the operator completes disconnection of the elbow 16 from the equipment bushing 14, the elbow 16 is placed upon a parking station available on the cabinet panel 12.
From the above description of the known operating system 10, it is apparent that there is no grounding of the cable 18 during use of the tool 30. Therefore, the operator(s) are placed at great risk in the event the cable 18 is accidently re-energized during this time.
In light of the foregoing, it is evident that there is a need in the art for a safe-operating load reducing tap plug which ensures continual grounding of the elbow connector during its disconnection from the equipment bushing. Moreover, there is a desire in the art for a disconnection process which only requires the use of one person in a line crew.